Telephone system



May 16, 1933. G. T. WARMOES ET AL TELEPHONE SYSTEM 2 Sheets-Shaet 1 Filed Jan. 8, 1932 INVENTORS G. 7. WARMOES JRAF ESCANDE BY ATTORNEY May 16, 1933. G. T. W-ARMOES ET AL TELEPHONE SYSTEM Filed Jan. 8, 1952 2 Sheets-Sheet 2 J A5. A. F ESCANDE By lNl/EN TORS Fillil III lnllll:

Jle. 8% {mm A T TOR/V5 Y Patented May 16, 1933 nniransrATEs PATENT OFFICE GUSTAVE 'r. wARMoRs AND JEAN R. A. F. nscANnn, or PARIS, FRANCE, ASSIGNORS TO WESTERN nLnorRic COMPANY, INCORPORATED, on NEW YORK, n. Y., A coRroRA- TION OF NEW YORK TELEPHONE SYSTEM Application filed January 8, 1932, Serial No. 585,496, and. in France March 6, 1931.

This invention relates to telephone systems and more particularly to trunk testing facilities for use in asystem in which a number of offices may be interconnected one with the other. Insuch a system, there is always provided a number of trunk lines for interconnecting the various offices, which number is determined by the volume of trafiic between the offices involved. The present invention 0 provides means whereby any one of these trunks may be tested from a convenient point in the network which may be at some distance from the originating and terminating points of these trunks.

The testing of trunk lines, espcially those which interconnect automatic or semi-auto-.

. enchange system. .-Various methods and means are at present employed to accomplish this result. Chief among these trunk testing facilities may be mentioned manual or automatic trunk test boards in each office which have accessibility to all outgoing trunks. It is to be expected, however, that as the automatic telephone artl develops to the point where variousoffices are consolidated in a single network of trunks radiating from main or tandem centers to each of the particular offices in the network, similar necessity for economies will dictate the consolidation of routine testing facilities for all the trunks in the network-in one central point from which all the trunks of the system can'be reached and tested. With the centralized testing of interoffice trunks, as shown by our invention, the special testing facilities such as manual or automatic trunk test boards now necessary in each office can be dispensed with and a common point of testing accessibility to all trunks can replace them, thereby resulting in decided economies of equipment, centralization of routine test records forall the trunks in the system and the further centralization of. control in one office for better correlated performance of the entire trunk network of the system. In accordance with our invention therefore, one specific embodiment of which is disclosed herein by way of illustration. This is accomplished in the following improved'mam ner.

The operator at the main testing oflice desiring to test a trunk outgoing from one ofthe ofices of the network, connects a dialing cord to a trunk which connects the main testing office with the office in which is located the outgoing end of the trunk to be tested and, by means of the cord dial further extends the connection to a switch which has access to all the interofiice trunks outgoing from that oflice. Two further digits set the brushes of the final, selector to a terminal allotted to the group containing the desired outgoing trunk whereupon a marking relay operates to mark the groupon a set of termi- "nals in the trunk test selector. Two further digits'from the cord dial set a'marker switch so as to marl: a particular set of terminals on another level of the test trunk selector and the terminal in the group previously identified will now be selected by the trunk selector. Two digits are necessary since the groups usually exceed ten in number although the invention may be easily modified to suit any group of trunks. The operator will now be connected to the desired trunk and may perform any tests thereon which are deemed necessary.

A clearer conception of the scope and purposes of our invention maybe obtained from the following detailed description taken in connection with the attached drawings in which: I

Fig. 1 shows a schematic layout of the system incorporating the invention wherein M represents the main testing office and K, L

testing office M fortesting interoflice trunks;

and Fig. 3 shows aninteroflice test trunk se-' lector circuit which maybe used at the central oflice K, L or G for testing purposes.

It is thought that the invention will be best understood by first considering the layout diagram shown in Fig. 1.

Referring to Fig. 1, therefore, four central ofices M, K, L and G are shown each representing an otfice of different subscriber capacity. The switches which are ordinarily employed for extending connections are indicated in the various ofiices and, in addi tion, the switches employed for testing purposes have also been indicated.

Although the central oifices indicated have been shown interconnected by single interofiice trunks in either direction, it is understood that, in actual practice, a plurality of such interoifice trunks between each pair of central ofi'ices are preferably employed. The switches A. and Y in each Ofiice are incoming selectors, the switches B, C, D are local group selectors, there being as many switches of each designation as the subscriber capacity of the ofiice warrants, while switch E in each oifice is a switching device for accessibility to all outgoing trunks.

Ordinarily if a call. is to be extended from the main testing central oifice M to central ofiice L the switch A in the central oifice K uses the first free outgoing trunk leading to the ofiice L, such as 100, but no indication will be given as to which trunk is taken into use.

But if, say, a particular trunk between K and L is to be tested from M, say 100, the operator at M is able to select the desired trunk by connecting the dialing cord 205 to an outgoing trunk from the main office to K, such as 102, and then dialing a number corresponding to the trunk which it is desired to test, it being understood that a special number is allotted to each trunk as a test number at the main testing ofiice M. Consequently. when the number is dialed by the operator, the connection will be extended from the cord to the switch A and thence to final selector D. which selects a line leading back to the switch E under the control of dialing impulses. Switch E is multipled to switch A and switch B and since B has access to trunks outgoing from K the dialing of further digits will. cause switch E to select the trunk which it is desired to test.

The same procedure may be adopted when it is desired to test other trunk lines extending to, say, central oifice G, when the par ticular trunk will be selected by the switch E in central ofiice L in response to the last twodigits. The switches in the various offices are multipled together in such a way as to allow the selection of a trunk leading back to the preceding office when desired.

Referringnow to Figs. 2 and 3, the circuits of the switch represented by switch E (or E or E") in Fig. 1 are shown together with an operators dialing cord circuit which will be located in the central office M, the circuits of switch E being shown in Fig. 3 and those of the cord circuit in Fig. 2.

The dialing cord circuit includes a dial 203, controlling relays 200 and 202, a supervisory lamp 201, it being understood that the operators head set OTC will be connected up over the condensers 206 and 207. The cord circuit terminates inthe plug 205 which may be associated with the jack 204: whose terminals are connected to the conductors of the outgoing trunk. These trunk conductors are shown connected at their incoming end to the brushes of the first group selector of the distant oifice, that is, switch A of Fig. l which extends the line ultimately to the brushes of the final selector (switch D of Fig. 1 )which has access to the circuit shown in Fig. 3, that is, switch E of Fig. 1.

Switch E comprises a set of group relays 303, 303, etc., a marker switch 340 having three contact arcs cooperating, respectively, with brushes 319, 320 and 321, a test trunk finder switch 3 11 having five contact banks each cooperating, respectively, with brushes 322, 323, 324:, 325 and 326, and a number of relays for controlling the operation of the circuit. The levels cooperating with brushes 322, and 323 and 324 of the test trunk finder are multipled to the banks of the A switches as indicated in Fig. 1 so that the test trunk finder 341 has access to all the trunks appearing in the A switches. The trunks are divided into groups corresponding to the groups appearing on the banks of the A switches and these groups are indicated on the level cooperating with brush 325 of the test trunk finder in which all the terminals of each group are multipled together. Each group of multipled terminals on the bank cooperating with brush 325 is connected to a corresponding top inner front contact of a relay 303, 303, etc., there being as many group relays as there are groups 01" trunks. The windings of the group relays are connected to the different terminals on the level cooperating with brush 302 of the final selector D, while the terminals of the levels cooperating with brushes 300 and 301 are multipled to the armatures of relay 308. The terminals of the level cooperating with brush 326 or" the test trunk finder 341 are divided into groups corresponding to the groups on the level associated with brush 325, but each corresponding terminal in each group is strapped to a selected terminal in the are as sociated with brush 320 of the marker switch 34-0, 01', if suificient terminals are not available on this are, to a terminal in the areassociated with brush 321, relay 31.3 being provided. for changing the connections from the are associated with brush 321 to that associated with are 320 when the digits assigned to a trunk line marked from the arc associated with the later brush have been dialed. The group relays such as 303, 303 are connected as shown, the dotted lines signifying connections made in series.

A detailed operation of the circuits will now be considered. When it is desired to test a trunk outgoing from a distant ofiice and not directly connected with the main testing ofiice M, the operator at office M inserts the plug 205 into the jack 20% of afree trunk outgoing to that distant ofiice from which a connection may be established to the office wherein is located the originating end of the trunk to be tested. Battery and ground are then connected through thewindings of relay 200 to conductors 334 and 335 of said free trunk. For the purpose of illustration, it will be assumed that a trunk connecting offices K and L is to be tested from ofiice M. When the incoming selector A at the distant office K is ready, a loop is closed in the well-known manner which causes the operation of relay 200. It is not thought necessary to describe the operation of the incoming selector at the distant oilice as such an operation is well known to the art and need not be repeated here. Relay 200 closes the circuit of lamp 201 which, upon lighting, signifies to the operator that she may commence dialing the necessary digits for setting the distant selectors at office K for reaching the switch E.

During the sending of the impulses by means of the dial 203, the off-normal condiion of the dial closes an obvious circuit for relay 202 which operates and, over its inner contacts connects direct ground to conductor 335 while, over its outer contacts, it short circuits the left winding of relay 200 and thereby connects low resistance battery to con-' ductor Relay 200 releases and extinguishes lamp 2-01. The digits are sent, in turn, to the group selectors and to set the final selector D at the distant ofiice K to select a trunk terminating in switch E which connects the wipers of switch D with the group containing the trunk to be tested, whereupon ground is connected from a circuit associated with conductor 302 to the winding of the particular group relay affected, such as relay 303. Relay 303 operates and, over its top inner contacts, connects direct ground to conductor 336 while over its top middle inner contact connects ground to conductor 337 which marks on the level cooperating with brush 325 of test trunk finder 341 the group containing the desired trunk. Ringing current connected from the final selector D to the line causes a circuit to be closed for relay 311 from one side of the ringing circuit in final selector D (or in the incoming selector A or B depending on the specific design of the circuit structure), conductor 301, conductor 338, right inner back contacts of relay 308, left inner back contacts of relay 306 winding of relay 311, condenser 3&0, right outer back contacts of relay 306, right-outer back contacts of relay 308, conductor 339, conductor 300 to the other side of the ringing circuit in final selector D or incoming selectors C or B. Relay 311 operates and closes an obvious circuit for operating slow-release relay 312. Relay 312 closes a circuit to magnet 305 of marker switch 340 from ground'on the front contacts of relay 312, left inn-er back contacts of relay 316, left outer back contacts of relay 306, left winding of magnet 305 to ground, A parallel path is also closed for operating slow-release relay 318 starting at the left outer back contacts of relay-306,'left outer contacts of relay 316, winding of relay 318 to battery.v Switch magnet 305 and relay 313 both operate. During the ringing period a tone is induced over the talking circuit back to the operators telephone circuit in the known manner. When the silent period of the ringing cycle is reached, relays 311 and 312 release and the marker switch 340 takes a step thereby advane-ing its associated brushes 319, 320 and 321 one step. In the present embodiment of the invention three steps are made in this manner to allow the test operator at the testcontacts of relay 317, brush 320 and cooper- V atin third terminal, left outerback contacts relay 308, right winding-of relay: 306 to battery, Relay 306 operates and in so doing disconnects the winding of magnet 305 from the ground on the front cont-act of relay 312, disconnects the Winding of relay 311 from the trunk conductors-33S and 339, and connects the circuit of the impulsing relay 307 across the line at the right inner back contacts of relay 308 to conductor 338 and right outer front contacts of relay 306, right outer back contacts of relay 308 to conductor Bela 318 also releases. The connection of the impulsing relay 307 causes the operation of the ring cut-off relay in the selector sup plying ringing current in the well-known manner. Relay 306 looks over its left Nillliling in a circuit from battery through its left winding, top outer normally made contacts of relay 317, right outer contacts of relay 306,1 conductor 336. toground on the top inner front contacts of relay 303.

#Vith the operation of the ring cut-off relay, the loop to the main office including rclay 307 in the distanto'llice and relay 200 of from the operators dial, relay 307 responds and, in releasing during the openperiod of an impulse, closes a circuit for operating the magnet 305 of the marker switch 340 from battery, through the left winding of magnet 305, left contacts of relay 307, right inner contacts of relay 306, back contacts of relay 318, left inner back contacts of relay 308, conductor 336, to ground on the top inner front contacts of relay 303. Relay 312 is operated in a parallel circuit from battery through its winding, left outer front contacts of relay 306, to the operating ground for magnet 305. \Vith each impulse, switch 340 tallies a step but relay 312, being slow to release, does not fall back during the reception of the train of impulses. At the end of the first train of impulses, relay 312 releases and, over its back contacts, closes a circuit for relay 316 over the right inner normally made contacts of relay 316, switch are cooperating with brush 319, brush 319, top outer back contacts of all the normal group relays 303, etc., top outer front contact of group relay 300, winding of relay 316 to battery. Relay 316 operates and locks over the traced operating path to ground over the right inner middle front contacts of said relay. Now, if the desired trunk has a test number of such a "value as to be designated on the marker switch arc cooperating with brush 320, the first train of impulses will direct brush 320 to the terminal connected to a conductor such as 342 thereby closing a circuit from ground on the back contacts of relay 312, top inner back contacts of relay 317, brush 320 and cooperating terminal, conduc tor 342, bottom middle contacts of relay 317, winding of relay 313 to battery. Relay 313 operates and locks over its left contacts to ground on the right inner front contacts of relay 316. If, however, the trunk to be tested is designated on the are cooperating with brush 321, the first train of impulses directs the marker switch 340 to a different terminal and relay 313 is not operated.

When the second train of impulses commences, relay 312 again operates as described and closes the following circuit to the winding of relay 317: battery through the winding of said relay, left inner front contacts of relay 316, to ground on the front contacts of relay 312. Relay 317 operates and locks in a circuit traced over its bottom inner contacts to ground on the right inner front contacts of relay 316 and, in breaking top outer, continuity contacts, opens the original locking circuit of relay 306 and transfers the holding path of this relay by way of the top outer front contacts of relay 317, back contacts of relay 318, left inner back contacts of relay 308 to ground on conductor 336.

Relay 307 responds to the second train of impulses which again steps the marker switch 340 and causes it to advance brushes 319, 320 and 321 to the terminal corresponding to the number of the wanted trunk. When the train of impulses is completed, re-

lay 312 releases and closes a circuit from ground on its back contacts, top inner frontcontacts of relay 317, left inner back contacts of relay 314, winding of relay 318 to battery. Relay 318 operates and, by the breaking of its back contacts opens the holding circuit of relay 306 which releases. The circuit of relay 307 as well as that of relay 200 is opened and lamp 201 is extinguished to indicate to the operator that selection is takin place. 7

Relay 318, over its front contacts, closes a circuit for magnet 315 of testtrunk finder 341 which is traceable as follows: ground on v conductor 336, left inner back contacts of relay 308, front contacts of relay 318, right outer contacts of relay 316, right back contacts of relay 314, winding of magnet 315 to battery. The switch magnet operates to advance brushes 322, 323, 324, 325 and 326 in search of the trunk group containing the trunk, the "number of which in th group has been sent. The test circuit is from ground on conductor 337 to the bank level cooperating with brush 325. When the brush-set reaches the first terminal of the required group, further selection takes place by test trunk finder 315 for the actual trunk whose number has been sent. As already described, the individual trunks of all groups are correspondingly multipled together and marked either by the are cooperating with brush 321 or that cooperating with brush 320. Consequently,

a test circuit is completed from ground on conductor 337, brush 325 and cooperating terminal, brush 326 and cooperating terminal, brush 321 and cooperating terminal, (if the trunk is marked on this are) right back contacts of relay 313, winding of relay 314 to battery. If on the other hand the trunk is marked on the are cooperating with brush 320, the test circuit is completed through brush 326 and cooperating terminal, conductor 343, brush 320 and cooperating terminal, bottom outer contacts of relay 317, right front contacts of relay 313, winding of relay 314't0 battery.

Then the test trunk finder switch 341 reaches the terminal of the trunk marked by switch 340 the circuit for test relay 314 is closed and this relay operates and opens the circuit of magnet 315 causing switch 341 to stop. With the operation of relay 314, the circuit is also opened to the winding of relay 318. This relay, however, being slow to release, releases only after an interval and in the meanwhile the trunk is tested for its busy or idle condition. if the trunk is busy a ground is connected to conductor 329 by the busying circuit in the incoming selector; otherwise a battery potential is present on the same conductor.

If the desired trunk is found to be idle the following path is closed to both windings in series of relay 310: ground on conductor 336, left inner back contacts of relay 308, front contacts of relay 318, right outer contacts of relay 316, right front contacts of relay 314, left winding of relay 310, right winding of said relay, brush 324, testing conductor 329 of the desired trunk, to battery. Relay 310 energizes over both its windings in series and locks up over its right winding in series with the winding of relay 309 to ground on its left contact, which relay also operates. The winding of relay 309 is now connected in parallel to both windings of relay 310 and thereby establishes a low potential busy test M circuit to protect the trunk from seizure by a hunting selector. 7 Relay 309 in turn operates relay 308 over an obvious circuit. Relay 308, on operating, opens the circuit of relay 306, and, loops the M talking conductors 330 and 331 by way of brushes 322 and 323 and the right outer and inner front contacts of relay 308 respectively. From this moment on the operator at the main testing oilice is connected to the M wanted trunk and must await before sending further impulses until the supervisory lamp again lights as an indication that the trunk is closed through at its termmatmg end.

If, on the other hand, relay 310 isshunted over the circuit previously traced to ground on conductor 329 and therefore relays 310, 309-and .308 do not operate and the trunk is found to be busy, ground is connected to the right winding of relay 306 overthe fol- ,"lowing path: ground on the'back contacts of relay 312, top' inner front contacts of relay 317, left inner front contacts of relay 314, left outer back contacts of relay 308, r1ght winding of relay 306 to battery. Relay 306 lnoperates and recloses the loop to the mam oilice through the winding of relay 307 to the main office and connects busy tone BT over a path from source of tone BT, condenser 343, left outer contacts of relay 314, "right contacts of relay 307, right inner back "contacts of relay 308, conductor 338, the previously described loop including the operators telephone circuit OTC, right contacts of the dial 203, left winding of relay 200, to battery. The operator, upon hearing the so busy tone, sends one impulse, if she desires to test the next trunk, whereupon marker switch 340 takes a step over as previously described, relay 314 releases and the test trunk infinder 341 advances to the next trunk after relay 318 has reoperated over a previously described circuit.

When the trunk or trunks have been tested and the connection to switch D is broken down, relay 303 is released by final selector 'D. Relay 30.3 opens the circuit to the left winding of relay 310 and the current flow ing through the winding of relay 303 and the right winding of relay 310 not being suflibient to hold relay310 operated, this relay "releases. Relay309 now releasesand,in

In the meanwhile, the release of relay 303 closed a return to normal path for the test trunk finder 341, from ground through the bottom outer contacts of relay 303,'the chain circuit through similar contacts of the group relays, off-normal contacts 344 of switch 341,

winding of magnet 315 to battery. 9 The switch operates to return the brushes 322 to 326 inclusive to the1r respective normal terminals on the bank at which time off-normal contacts 344 are openedand the switch magnet stops. All parts of the circuit are nownormal and ready to be reseized.

Should the operator desire to break down the connection at any time prior to dialing the trunk number code, that is, when the brushes of themarking switch are either on thesecond' or third terminal of their respec tive arcs, then the release of relay 303 will 1 cause the release of relay 317 as already de-' scribed and a path is closed for returning the marker switch 340 to normal. This path may be traced as follows: battery throu h theleft winding of magnet 305, interrupter contacts, top outer back contacts of relay 303 c and the series chain of top outer contacts of the remaining group relays including 303, similar chain over the bottom inner back contaots of the same group of relays, the second or third terminals on the are cooperating with brush .320, top inner back contacts ofrelay 317, to ground on the back contacts of relay 312. The'switch brushes are advanced by this circuit tothe'fourth terminal of their respective arcs from which they are then returned to normal as previously described.

lVhat is claimed is:

1. A telephone system comprising a main testing oflice, a plurality of other oflices, trunk lines interconnecting each of said oilices andsaid main testing oflice, means for establishing an operative connection between said main testing oflice and anyone of said plurality of otfices, and means at said main testing office for controlling over said connec-' tion the selection of anyone of saidtrunk lines interconnecting said oilice with said main office.

2. Atelephone system comprising a main testing oflicefa plurality of'. other offices, trunk lines interconnecting each of said offices with the other offices and with said main testing office, means for establishing an operative connection between said main testing office and any one of said plurality of offices, and means at said main testing office for controlling over said connection the selection of any one of said trunk lines interconnecting said ofiice with any other office.

3. A telephone system comprising a main testing office, a plurality of other offices, trunk lines interconnecting each of said offices with the other offices and with said main testing office, means for establishing an operative connection between said main testing office and any office of said plurality of offices, con trol means at said main testing office, and switching means at the office operatively connected therewith responsive to said control means for selecting over said established connection one of said trunk lines interconnect ing said office with any other office.

- 4:. A telephone system comprising a main testing office, a plurality of offices, a plurality of trunk lines each having an arbitrary designation interconnecting said plurality of offices with each other and with said main testing office, means for establishing an operative connection between said main testing office and any one of said plurality of offices, control means at said main testing office, and 9. switching means at the office operatively connected therewith responsive to said control means for selecting a trunk line at said office in accordance with the arbitrary designation of said trunk line.

5. A telephone system comprising a. main testing office, a plurality of other offices, a plurality of trunk lines interconnecting said plurality of offices with each other, each of said trunk lines having an impulse code des- Tignation, an impulse sending device at said main testing office, impulse responsive switches at each of said offices for selecting said trunk lines originating in said offices, means for establishing an operative connec- 4 tion between said main testing office and any one of said offices under the control of said impulse sending device and means responsive to the transmission thereover of an impulse code corresponding to the arbitrary designa- 5 tion of a trunk originating in said office for operating said switch to extend said connection from said main testing office to said trunk.

6. A telephone system comprising a main 'testing office, a plurality of other offices, a

plurality of trunk lines each having an impulse code designation for interconnecting said offices with each other and with said main testing office, connection extending fswitches in each of said offices, an impulse sending device in said main testing office, an impulse responsive switching device in each of said offices for selecting said trunk lines originating in each of said offices, means under the control of said impulse sending device. for establishing an operative'connection between said main testing office and saidswitching device in any one of said ofiices plurality of trunk lines each having an im pulse code designation interconnecting said offices with each other and with said main testing office, means for establishing an operative connection between said main testing office and any one of said plurality of offices, supervisory means at said main testing office, impulse sending means at said main testing office, and switching means at the office connected therewith responsive to said impulse sending means for selecting a trunk line originating at said office in accordance with the impulse code designation of' said trunk, and means responsive to the condition of said trunk for operating said supervisory means in said main testing office.

8. A telephone system comprising a main testing office, a plurality of other offices, a plurality of trunk lines each having an impulse code designation interconnecting said ofiices with each other and with said main testing office, means for establishing an operative connection between said main testing office and any one of said plurality of offices, an operators telephone circuit at said main testing office operatively associable' with said connection, impulse sending means at said main testing office, switching means at the office connected therewith responsive to said impulse sending means for selecting a trunk line originating in said office in accordance with the impulse code designation of said trunk, and means responsive to the busy condition of said trunk for establishing a busy tone circuit over said established connection to said operators telephone circuit.

9. A telephone system comprising a main testing office, a plurality of other offices, a plurality of trunk lines each having an impulse code designation interconnecting said offices with each other and with said main testing office, connection extending switches in each of said offices, a source of ringing current associated with said switches, a switching device in each of said offices comprising a marking switch and a trunk selector for selecting said trunk lines originating in said offices, means for establishing an operative connection between said main testing ofiice and said switching device in any of said offices through said connection extending switches of said office, means responsive to said connection for setting said marking Cal switch from said ringing current source, and means at said main testing ofiice responsive to the setting of said marking switch for operating said trunk selector to select a trunk line originating in said oilice in accordance with the impulse code designation of said trunk line.

10. In a telephone system comprising a main testing oilice, a plurality of other oflices, a plurality of trunk lines interconnecting each or" said olfices and said main testing ofiice, each of said trunk lines having an impulse code designation, an impulse sending device and supervisory means at said main testing oiiice, an impulse responsive switch at each of said ofiices for selecting said trunk lines originating therein, means controlled by said impulse sending device for establishing an operative connection between said main testing ofiice and any one of said oirices, means responsive to the transmission thereover from said impulse sending device of an impulse code corresponding to the desi nation of a trunk originating in said office or operating said switch therein to establish an operative connection between said main testing ofiice and said trunk, means responsive to the busy condition of said trunk for operating said supervisory means, and means thereafter reponsive to the transmission of another impulse from said main testing oflice for operating said switch to establish an operative connection between said main testing ofiice and anothertrunk.

11. A telephone system comprising a main testing oilice, a plurality of other offices, a plurality of groups of trunk lines interconnecting each of said offices with each other and with said main testing oilice, each trunk line in each of said groups having an impulse code designation indicating its group and its location in that group, an impulse sending device at said main testing ofiice, an impulse responsive switch at each of said ofiices for selecting said trunk lines originating in said ofiices, means for establishing an operative connection between said main testing oflice and any one of said oflices, supervisory means in said main testing oflice, means responsive to the transmission over said connection of an impulse code corresponding to the designation of a trunk originating in said oflice for operating said switch to establish an operative connection between said main testing ofiice and said trunk, means responsive to the busy condition of said trunk for operating said supervisory means, and means responsive to the further transmission of an impulse designating a different trunk in the same group for operating said switch to establish an operative connection between said 7 main testing oflice and said difl'erent trunk in said same group.

12. In a trunk testing system, a plurality of oliices, a plurality of groups of trunks each having an impulse code designation interconnecting each of said oilices with the other offices, a switching device in each of said oflic'es comprising means for marking each trunk group, means responsive to an impulse code designation of a trunk. for marking each trunk, and means responsive to the operation of said group marking means and said trunk marking means for selecting the trunk designated by said group and trunk marking 1neans.-

13. In a trunk testing system, a plurality of ofiices, a plurality of groups of trunks each having an impulse code designation denoting the group and the location of a trunk in the group,n1eans for establishing a connection from one of said offices to any other of said:

ment of a connection from one of said officesto any other of said ofiices and the further transmission thereover of the impulse code of a trunk for operating in said other oiiice said trunk group marking means, said trunk marking means and said trunk selecting means for extending said connection to said trunk corresponding to said impulse code.

14. In a telephone system, a main testing miles, a plurality of other ollices, a plurality of groups of trunk lines interconnecting each of said ofiices with each other and with said main testing ofiic'e,each trunk line in each of said groups having an impulse code designation indicative of its group and its location in that group, connection extending switches in each of said ofiices, a switching device in each of said oilices comprising a test trunk finder having accessibility to groups of said trunk lines originating in said ofiices and a marker switch responsive to dial impulses, means including said connection extending switches for establishing an operative connection' between said main testing otfice and the switching device or" any of said offices, means for extending said operative connection to said marker switch, means in said main testing office for operating said marker switch in accordance with the impulse code of a wanted trunk and means responsive to the setting of said marker switch for operating said trunk finder to extend said operative connection to said wanted trunk.

15. In a telephone system, a main testing oiiice,a plurality of other offices, a plurality of groups of trunk lines interconnecting each of said offices with each other and with said main testing ofiice, each trunk line in each of said groups having an impulse code designation indicative of its group and its location in that group connection extending switches in each of said ofiices, a switching device in each of said o ifices comprisinga relay for each group of trunks originating in said otlice a test trunk finder having a plurality of contact arcs and cooperative brushes, said trunk finder further having accessibility to said trunk lines over some of said contact arcs, a marker switch having a plurality of contact arcs and cooperative brushes, some v of said contact arcs on said trunk finder and contact arcs of said marker switch being interconnected in accordance with the impulse code designation of corresponding trunks in all groups, means including said connection extending switches for establishing an operative connection between said main testing otfice and the switching device of any of said ofiices, means responsive to the operation of a trunk group relay for operating said trunk finder to connect with the first trunk of the group of trunks marked by said relay, and

means responsive to the setting of said marker switch in accordance with the impulse code of a trunk in said group for further operating said trunk finder to extend said operative connection to said trunk.

In witness whereof, we hereunto subscribe our names this 16th day of December, 1931.

GUSTAVE T. VVARMOES. JEAN R. A. F. ESCANDE. 

